If by "field" you mean a combobox or a listbox, you look at
the .RowSource property.
If the .RowSourceType is set to Value List, then you can
add more choices in the .RowSource using a semicolon as a
delimiter
If the .RowSourceType is set to Table/Query, then you have
to look at the table where the rowsource originates and add
it there.